Surgical tissue collection for pathology analysis to detect cancer cells from excised tissue has been the standard practice in cancer diagnosis for decades. The current protocols for tissue sample collection call for excised tissue to be collected and placed in a formalin solution, and then transported to the pathology laboratory for staining and analysis. Unfortunately, formalin fixes cells (e.g. kills the cells) and in the process causes significant changes in the cellular integrity which produces problems with the ability to accurately conduct genomic testing (RNA, mRNA and protein biomarker analysis, and gene expression studies) analyses.
Molecular technology, such as genomic testing with real-time polymerase chain reaction technology (RT-PCR), has evolved to the extent that certain cancers can be matched to specific chemotherapies that have been shown to respond to certain gene expression patterns found in the cancer cells. Thus, being able to obtain accurate gene expression patterns of the cancer cells excised from a patient allows for personalized healthcare by designing individualized chemotherapy as well as other treatments. This is a very important shift in treatment paradigms and will represent the standard of care in the near future.
Cancer tissue samples which have been preserved in formalin are not viable tissue samples for completing gene expression analyses. One reason formalin is not a good reagent for achieving gene expression analysis on tissue samples is that formalin causes the slow cross linking of proteins into a mesh network, and valuable target proteins may be destroyed by the formalin process as they are not protected from degradation.
Furthermore, as formalin penetrates the tissue sample, cell death (apoptosis) occurs. Cancer cells are unique as they have a metabolic pre-programmed apoptosis, thus accelerated apoptosis occurs in formalin. As the cells in the tissue sample die, a subset of the total cell population lyse and release a broad range of internal regulatory enzymes which further cause accelerated cell death. A number of these enzymes will degrade or destroy target nucleic acids DNA, RNA, mRNA, regulatory proteins, and associated biomarkers used in molecular genomic analysis. During the fixation process, while the formalin kills the cells in the tissue sample, gene expression can become erratic and genomic expression of critical genes can become under expressed or over expressed, giving inaccurate values of the expression of certain cancer genes. This is a major problem when chemo therapy decisions are based on the levels of specific mRNA from selected genes. Thus, accurate genomic testing of cancer cells fixed in formalin is not possible at present.
It should also be noted that fixing the proteins and cells in a tissue sample with formalin takes about 48 hours to occur. Making the formalin process not very exact at determining what the genetic expression is at the time of tissue collection from a patient.
In general, the scientific usefulness of genetic data obtained from tissue fixation is directly related to the quality of the tissue and the usefulness of that tissue for genomic testing. Presently, formalin fixation is not very useful in obtaining accurate genetic expression information. Thus there is a need for reagents for fixing tissue samples, so that the collected sample comprises accurate gene expression markers for genetic testing.
There is also a need for tissue sample fixation reagents that are not as hazardous as formalin. Unfortunately, formalin carries a significant risk of cancer to the users, as well as significant state and federal regulations for the use and disposal of the products containing formalin.
The present invention discloses methods for manufacturing reagents and the composition of reagents which allow for the collection of cancer tissue surgically removed from a patient, in which the genetic cellular information of the cancer cells in the tissue sample are maintained in a viable state, making the tissue sample suitable for genetic expression analysis.